Towards Addressing Spatio-Temporal Aspects in Security Games

Abstract:

Game theory has been successfully used to handle complex resource allocation and patrolling problems in security and sustainability domains. More specifically, real-world applications have been deployed for different domains based on the framework of security games, where the defender (e.g., security agency) has a limited number of resources to protect a set of targets from an adversary (e.g., terrorist). Whereas the first generation of security games research provided algorithms for optimizing security resources in mostly static settings, my thesis advances the state-of-the-art to a new generation of security games, handling massive games with complex spatio-temporal settings and leading to real-world applications that have fundamentally altered current practices of security resource allocation. Indeed, in many real-world domains, players act in a geographical space over time, and my thesis is then to expand the frontiers of security games and to deal with challenges in domains with spatio-temporal dynamics. My thesis provides the first algorithms and models for advancing key aspects of spatio-temporal challenges in security games, including (i) continuous time; (ii) continuous space; (iii) frequent and repeated attacks; (iv) complex spatial constraints. First, focusing on games where actions are taken over continuous time (for example games with moving targets such as ferries and refugee supply lines), I propose a new game model that accurately models the continuous strategy space for the attacker. Based on this model, I provide an efficient algorithm to calculate the defender’s optimal strategy using a compact representation for both the defender and the attacker’s strategy space. Second, for games where actions are taken over continuous space (for example games with forest land as a target), I provide an algorithm computing the optimal distribution of patrol effort. Third, my work addresses challenges with one key dimension of complexity – frequent and repeated attacks. Motivated by the repeated interaction of players in domains such as preventing poaching and illegal fishing, I introduce a novel game model that deals with frequent defender-adversary interactions and provide algorithms to plan effective sequential defender strategies. Furthermore, I handle complex spatial constraints that arise from the problem of designing optimal patrol strategy given detailed topographical information. My thesis work has led to two applications which have been deployed in the real world and have fundamentally altered previously used tactics, including one used by the US Coast Guard for protecting the Staten Island Ferry in New York City and another deployed in a protected area in Southeast Asia to combat poaching.